// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// See net/disk_cache/disk_cache.h for the public interface.

#ifndef NET_DISK_CACHE_BLOCKFILE_BLOCK_FILES_H_
#define NET_DISK_CACHE_BLOCKFILE_BLOCK_FILES_H_

#include <stdint.h>

#include <memory>
#include <vector>

#include "base/files/file_path.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "net/base/net_export.h"
#include "net/disk_cache/blockfile/addr.h"
#include "net/disk_cache/blockfile/disk_format_base.h"
#include "net/disk_cache/blockfile/mapped_file.h"

namespace base {
class ThreadChecker;
}

namespace disk_cache {

// An instance of this class represents the header of a block file in memory.
// Note that this class doesn't perform any file operation (as in it only deals
// with entities in memory).
// The header of a block file (and hence, this object) is all that is needed to
// perform common operations like allocating or releasing space for storage;
// actual access to that storage, however, is not performed through this class.
class NET_EXPORT_PRIVATE BlockHeader {
public:
    BlockHeader();
    explicit BlockHeader(BlockFileHeader* header);
    explicit BlockHeader(MappedFile* file);
    BlockHeader(const BlockHeader& other);
    ~BlockHeader();

    // Creates a new entry of |size| blocks on the allocation map, updating the
    // apropriate counters.
    bool CreateMapBlock(int size, int* index);

    // Deletes the block pointed by |index|.
    void DeleteMapBlock(int index, int block_size);

    // Returns true if the specified block is used.
    bool UsedMapBlock(int index, int size);

    // Restores the "empty counters" and allocation hints.
    void FixAllocationCounters();

    // Returns true if the current block file should not be used as-is to store
    // more records. |block_count| is the number of blocks to allocate.
    bool NeedToGrowBlockFile(int block_count) const;

    // Returns true if this block file can be used to store an extra record of
    // size |block_count|.
    bool CanAllocate(int block_count) const;

    // Returns the number of empty blocks for this file.
    int EmptyBlocks() const;

    // Returns the minumum number of allocations that can be satisfied.
    int MinimumAllocations() const;

    // Returns the number of blocks that this file can store.
    int Capacity() const;

    // Returns true if the counters look OK.
    bool ValidateCounters() const;

    // Returns the identifiers of this and the next file (0 if there is none).
    int FileId() const;
    int NextFileId() const;

    // Returns the size of the wrapped structure (BlockFileHeader).
    int Size() const;

    // Returns a pointer to the underlying BlockFileHeader.
    BlockFileHeader* Header();

private:
    BlockFileHeader* header_;
};

typedef std::vector<BlockHeader> BlockFilesBitmaps;

// This class handles the set of block-files open by the disk cache.
class NET_EXPORT_PRIVATE BlockFiles {
public:
    explicit BlockFiles(const base::FilePath& path);
    ~BlockFiles();

    // Performs the object initialization. create_files indicates if the backing
    // files should be created or just open.
    bool Init(bool create_files);

    // Returns the file that stores a given address.
    MappedFile* GetFile(Addr address);

    // Creates a new entry on a block file. block_type indicates the size of block
    // to be used (as defined on cache_addr.h), block_count is the number of
    // blocks to allocate, and block_address is the address of the new entry.
    bool CreateBlock(FileType block_type, int block_count, Addr* block_address);

    // Removes an entry from the block files. If deep is true, the storage is zero
    // filled; otherwise the entry is removed but the data is not altered (must be
    // already zeroed).
    void DeleteBlock(Addr address, bool deep);

    // Close all the files and set the internal state to be initializad again. The
    // cache is being purged.
    void CloseFiles();

    // Sends UMA stats.
    void ReportStats();

    // Returns true if the blocks pointed by a given address are currently used.
    // This method is only intended for debugging.
    bool IsValid(Addr address);

private:
    // Set force to true to overwrite the file if it exists.
    bool CreateBlockFile(int index, FileType file_type, bool force);
    bool OpenBlockFile(int index);

    // Attemp to grow this file. Fails if the file cannot be extended anymore.
    bool GrowBlockFile(MappedFile* file, BlockFileHeader* header);

    // Returns the appropriate file to use for a new block.
    MappedFile* FileForNewBlock(FileType block_type, int block_count);

    // Returns the next block file on this chain, creating new files if needed.
    MappedFile* NextFile(MappedFile* file);

    // Creates an empty block file and returns its index.
    int16_t CreateNextBlockFile(FileType block_type);

    // Removes a chained block file that is now empty.
    bool RemoveEmptyFile(FileType block_type);

    // Restores the header of a potentially inconsistent file.
    bool FixBlockFileHeader(MappedFile* file);

    // Retrieves stats for the given file index.
    void GetFileStats(int index, int* used_count, int* load);

    // Returns the filename for a given file index.
    base::FilePath Name(int index);

    bool init_;
    char* zero_buffer_; // Buffer to speed-up cleaning deleted entries.
    base::FilePath path_; // Path to the backing folder.
    std::vector<MappedFile*> block_files_; // The actual files.
    std::unique_ptr<base::ThreadChecker> thread_checker_;

    FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_ZeroSizeFile);
    FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_TruncatedFile);
    FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_InvalidFile);
    FRIEND_TEST_ALL_PREFIXES(DiskCacheTest, BlockFiles_Stats);

    DISALLOW_COPY_AND_ASSIGN(BlockFiles);
};

} // namespace disk_cache

#endif // NET_DISK_CACHE_BLOCKFILE_BLOCK_FILES_H_
